On Tue, Jul 31, 2012 at 04:07:23PM +0200, Lluís Batlle i Rossell wrote: > Maybe there could be a cleaner declaration of that intention, though. The only > code there was "I herewith declare: this does not happen. So send SIGBUS." To give you an idea, the emulation is on the order of a 1000 times slower than the processing a properly aligned load in hardware. And even where hardware does unaligned handling such as on x86 there still is a performance penalty though that would far less severe. So given that proper alignment is always the right thing. There are very few cases were handling misalignment in software is justified, for example the IP stack. Even the checks if a packet is misaligned would cause a performance penalty and it's (assuming sane networking hardware) a very rare event. lwl/lwr in the IP stack would be a bad tradeoff. It's faster than the unaligned exception handler but would slow down processing of every correctly aligned packet. So lwl/lwr are only a good choice where a high fraction of misaligned packets is expected. Ralf
